Various types of winter garments, interiors, and leisure goods having increased heat retaining effects have been proposed and implemented. There are two main methods of increasing heat retaining effects. In the first method, the dissipation of heat generated from the human body is reduced, and heat retention properties are maintained by such methods as controlling the weave and knit structure in the winter garment or making the fibers hollow or porous, for example, to physically increase the number of air layers in the winter garment. In the second method, heat is accumulated and heat retention properties are enhanced in the winter garment, for example, by such active methods as chemically/physically processing the garment as a whole or the fibers that constitute the winter garment so as to radiate the heat generated from the body back towards the body, convert a portion of the sunlight received by the winter garment into heat, and produce other effects.
Methods such as increasing the number of air layers in the garment, increasing the thickness of the fabric, increasing the fineness of the weave, or darkening the color have been employed as examples of the first category of methods described above. These methods are used in sweaters and other garments that are used in winter, for example. In garments that have been widely used as winter sports apparel, for example, an inner filling is provided between the outer layer and the lining, and heat retention properties are maintained by the thickness of the air layer of the inner filling. However, the garment becomes heavy and bulky when an inner filling is added, making the garment unsuitable for sports that require freedom of movement. In order to overcome these drawbacks, methods in the above-mentioned second category have recently come into use that actively and effectively utilize internally generated heat and external heat.
One type of method for implementing the second category of methods includes known methods whereby aluminum, titanium, or another metal is deposited on the lining or the like of a garment to actively prevent the emanation of heat by using the metal deposited surface to reflect heat that is radiated from the body. However, not only is it considerably expensive to vapor deposit a metal in the garment by these methods, but uneven deposition and other defects reduce the manufacturing yield, which effectively raises the price of the product itself.
Another method that has been proposed as an implementation of the second category of methods involves kneading alumina, zirconia, magnesia, and other ceramic particles into the fibers as such to utilize the far infrared radiating effects or photothermal conversion effects of the inorganic microparticles, i.e., to actively absorb external energy.
For example, Patent Document 1 describes a technique in which inorganic microparticles of silica, barium sulfate, or the like having heat radiating characteristics are prepared that include at least one type of species selected from metal ions and metals that have a heat conductivity of 0.3 kcal/m2·sec·C° or higher, heat radiating fibers are manufactured that include one or more types of the inorganic microparticles, and the fibers are used to enhance heat retention properties.
Patent Document 2 discloses that excellent heat retention properties are demonstrated in a fiber that includes aluminum oxide microparticles as well as ceramic microparticles contained in an amount of 0.1 to 20 wt % with respect to the fiber weight and capable of absorbing and converting light to heat and radiating far infrared rays.
Patent Document 3 describes the proposal of an infrared absorbing processed fiber article that is formed by dispersing and fixing an infrared absorbing agent composed of an amino compound, and a binder resin that includes an ultraviolet absorbing agent and various types of stabilizers that are used as needed.
Patent Document 4 proposes a near infrared absorption processing method for obtaining a cellulose-based fiber structure that absorbs near infrared rays (in the near infrared wavelength range of 750 to 1500 nm, wherein the spectral reflectance of the material is 65% or lower) by dyeing the structure with a combination of a dye and another dye that is selected from the group consisting of a substantive dye, a reactive dye, a naphthol dye, and a vat dye, whose absorption in the near infrared region is greater than that of a black dye.
In Patent Document 5, the present inventors propose a fiber that includes hexaboride microparticles as a heat absorbing component that is selected as a material that has high reflectance and low transmittance of light in the near infrared region in spite of having high transmittance and low reflectance of visible light. The inventors also propose a fiber article that is manufactured using the aforementioned fiber.
[Patent Document 1]: JP-A 11-279830
[Patent Document 2]: JP-A 5-239716
[Patent Document 3]: JP-A 8-3870
[Patent Document 4]: JP-A 9-291463
[Patent Document 5]: JP-A 2003-174548